Evaluation of a Candidate International Standard Preparation for Human Anti-Toxoplasma Immunoglobulin G

Evaluation of a Candidate International Standard Preparation for Human Anti-Toxoplasma Immunoglobulin G
November 2004
Peter Rigsby,1 Sjoerd Rijpkema,2* Edward C. Guy,3 Janet Francis,3 and Rose Gaines Das1
Informatics Laboratory,1 Division of Bacteriology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire,2 Toxoplasma Reference Laboratory, National Public Health Service for Wales, Swansea, United Kingdom3
Journal of Clinical Microbiology, November 2004, p. 5133-5138, Vol. 42, No. 11
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A freeze-dried human serum preparation containing immunoglobulin G (IgG) to Toxoplasma gondii was assessed for its suitability as an international reference reagent in an international collaborative study by 24 laboratories from 17 countries. This candidate standard was compared with the third international standard (IS) for human anti-Toxoplasma serum, TOXM, with the previous second IS, TOXS, and with a range of other serum samples. Samples were tested with the Sabin-Feldman dye test and a range of agglutination assays and enzyme immunoassays. This study emphasizes the need for appropriate standards if intermethod agreement of estimates is to be achieved. On the basis of the results of this study, the preparation was established by the World Health Organization as the first IS for human anti-Toxoplasma IgG, with an assigned potency of 20 IU per ampoule of total anti-Toxoplasma antibodies.